LED Structure

ABSTRACT

An LED structure includes a first substrate; an adhering layer formed on the first substrate; first ohmic contact layers formed on the adhering layer; epi-layers formed on the first ohmic contact layers; a first isolation layer covering the first ohmic contact layers and the epi-layers at exposed surfaces thereof; and first electrically conducting plates and second electrically conducting plates, both formed in the first isolation layer and electrically connected to the first ohmic contact layers and the epi-layers, respectively. The first trenches or the second trenches allow the LED structure to facilitate complex serial/parallel connection so as to achieve easy and various applications of the LED structure in the form of single structures under a high-voltage environment.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to LED structures, and more particularly,to a high-power LED structure operable in a high-voltage environment.

2. Description of Related Art

U.S. Pat. No. 6,853,011 has disclosed a light emitting epi-layerstructure containing a temporary substrate of absorption light type onone side while the other side thereof is then adhered to a transparentsubstrate of light absorption free by BCB bonding layer. After thetemporary substrate is removed, the resulted light emitting structure isthen patterned to form a connection channel to connect the first ohmiccontact electrode and form an isolation trench to separate the activelayer of the light emitting structure into two parts. Thereafter, asecond ohmic contact electrode on the cladding layer and a bonding metallayer filled in the first channel and on second ohmic contact electrodeare successively formed. The resulted LED structure is hence convenientfor flip-chip structure since two bonding metal layers have the samealtitude.

U.S. Pat. No. 6,998,642 has disclosed a semiconductor structure with twolight emitting diodes in series connection. The semiconductor structurecomprises two light emitting diodes (LEDs) having the same stack layersand abutting each other but spaced by an isolation trench. The stacklayers from a bottom thereof include a thermal conductive substrate, anonconductive protective layer, a metal adhering layer, a mirrorprotective layer, a p-type ohmic contact epi-layer, an upper claddinglayer, an active layer, and a lower cladding layer. Two p-type ohmiccontact metal electrodes for two LEDs are formed on an interface betweenthe mirror protective layer and the ohmic contact epi-layer and buriedin the mirror protective layer.

The stack layers have first trenches formed therein which exposes theupper cladding layer and electrical connecting channels to connectp-type electrodes. The isolation trench is formed by patterning theexposed upper cladding layer until further exposing the nonconductiveprotective layer. Two n-type electrodes are formed on the lower claddinglayer of two LEDs. A dielectric layer is deposited to fill the isolationtrench and covered a sidewall of the first trench so that it canelectrically isolate layers of the stack layers of the second LED whilea metal connection trace formed thereon to connect the p-type ohmiccontact electrode of the first LED and n-type of ohmic electrode ofsecond LED.

Although the structure of U.S. Pat. No. 6,853,011 is applicable toflip-chip structures, it would be impossible to connect two of the LEDstructures without assistance of submounts. Besides, complexity of theflip-chip process could be significantly increased because there arenumerous chips to be processed. On the other hand, while the structureof U.S. Pat. No. 6,998,642 enables the electrical connection betweenLEDs, metal-to-metal adherence where such electrical connection reliescould be only achieved through a complex process, resulting in problemsrelated to weak productivity and high manufacturing costs. Moreover,since the nonconductive layer is located at the boundary between theLEDs, the metal connection trace could only connect two electricallyconducting plates and it would still be impossible to achieve a circuitlayout with further complexity if no submounts are provided.

Thus, in view of the inconvenience and defects reflected in theirconfigurations and applications, the existing LED structures need to beimproved. Although all relevant manufactures have saved no efforts tosolve the aforementioned problems, an applicable approach has not beendeveloped. It is still a challenge for the manufacturers to provide anappropriate structure to all related products with the attempt solvingthe aforementioned problems. Hence, creation of a novel LED structurehas become an immediate R & D task and a common goal of the industry.

Considering the defects of the known LED structures, the inventor of thepresent invention, aiming at creating a novel LED structure that reformsthe defects of the existing LED structures and possesses improvedpracticality, and basing on his years of practical experience andprofessional knowledge in designing and manufacturing this product, hasapplied appropriate theories and performing active researches andinnovation. After unceasing researches and repeated retrofit, theinventor herein discloses the present invention that exactly providespractical utility.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a novel LEDstructure that remedies the defects of the conventional products whilefacilitating interconnection between LEDs and easy manufacture of an LEDsingle-structure that has improved elaborateness and is operable in ahigh-voltage environment, thus being more utility.

To achieve the objective of the present invention, the LED structureaccording to a first embodiment of the present invention comprises: afirst substrate having a first surface and a second surface; an adheringlayer formed on the first surface; at least two first ohmic contactlayers formed on the adhering layer; at least two epi-layers, wherein afirst trench is formed between each two adjacent said epi-layers, andeach said epi-layer includes: a lower cladding layer formed on one saidfirst ohmic contact layer; an active layer formed on the lower claddinglayer; and an upper cladding layer formed on the active layer; a firstisolation layer covering the first ohmic contact layers and the uppercladding layers at exposed surfaces thereof, and formed between each twoadjacent said first ohmic contact layers, wherein the first isolationlayer has first openings and second openings formed at the exposedsurfaces of the upper cladding layers and the first ohmic contactlayers, respectively; at least two first electrically conducting plates,each formed in one said first opening and electrically connected to onesaid upper cladding layer; and at least two second electricallyconducting plates, each formed in one said second opening andelectrically connected to one said first ohmic contact layer.

To achieve the objectives of the present invention and solve thetechnical problems of the prior arts, the following means are proposedin the present invention.

In the aforesaid LED structure, each of the first ohmic contact layersis a p-type ohmic contact layer.

In the aforesaid LED structure, the lower cladding layer is a p-typeAlGaInP cladding layer and the upper cladding layer is an n-type AlGaInPcladding layer.

In the aforesaid LED structure, the active layer is in a form of asingle hetero-structure (SH), a double hetero-structure (DH) or multiplequantum wells (MQW).

In the aforesaid LED structure, a second ohmic contact layer is formedbetween the upper cladding layer and the first electrically conductingplates.

In the aforesaid LED structure, the first substrate is a transparentsubstrate and the adhering layer is a transparent adhering layer, and amirror layer is formed on the second surface.

In the aforesaid LED structure, the adhering layer is a transparentadhering layer, and a mirror layer is formed between the first substrateand the adhering layer.

In the aforesaid LED structure, a submount has a third surface whereonat least two third electrically conducting plates and at least twofourth electrically conducting plates are formed, wherein the submountis formed with a plurality of traces for electrically connecting thethird electrically conducting plates and the fourth electricallyconducting plates, each of the third electrically conducting plates andthe fourth electrically conducting plates being electrically connectedto the corresponding first electrically conducting plate and/or thesecond electrically conducting plate via one or more solder joints, andthe first substrate being a transparent substrate while the adheringlayer being a transparent adhering layer.

In the aforesaid LED structure, a mirror layer is formed on the thirdsurface while not covering the third and fourth electrically conductingplates.

In the aforesaid LED structure, a mirror layer is formed on the firstisolation layer.

In the aforesaid LED structure, a first conductor layer is formed withat least one conductor and covers the first isolation layer, eachconductor having two opposite ends electrically connected to the secondelectrically conducting plate and the first electrically conductingplate of different units, respectively.

To achieve the objective of the present invention, the LED structureaccording to a second embodiment of the LED structure of the presentinvention comprises: a first substrate having a first surface and asecond surface; an adhering layer formed on the first surface; at leasttwo first ohmic contact layers formed on the adhering layer; at leasttwo epi-layers, wherein each said epi-layer includes: a lower claddinglayer formed on one said first ohmic contact layer; an active layerformed on the lower cladding layer; an upper cladding layer formed onthe active layer; and a second trench vertically passing through theupper cladding layer and the active layer and entering a part of thelower cladding layer; a second isolation layer covering the uppercladding layers and formed between each two adjacent said epi-layers andbetween each two adjacent said first ohmic contact layers, wherein thesecond isolation layer has a third opening formed on each said uppercladding layer and a fourth opening formed at an inner side of each saidsecond trench; at least two fifth electrically conducting plates, eachformed in one said third opening and electrically connected to one saidupper cladding layer; and at least two sixth electrically conductingplates, each formed in one said fourth opening, having an extendingportion extending downward to vertically pass through the epi-layer andelectrically connect with the first ohmic contact layer.

To achieve the objectives of the present invention and solve thetechnical problems of the prior arts, the following means are proposedin the present invention.

In the aforesaid LED structure, each of the first ohmic contact layersis a p-type ohmic contact layer.

In the aforesaid LED structure, the lower cladding layer is a p-typeAlGaInP cladding layer and the upper cladding layer is an n-type AlGaInPcladding layer.

In the aforesaid LED structure, the active layer is in a form of asingle hetero-structure (SH), a double hetero-structure (DH) or multiplequantum wells (MQW).

In the aforesaid LED structure, the second trench has the secondisolation layer formed therein.

In the aforesaid LED structure, a second ohmic contact layer is formedbetween the upper cladding layer and the fifth electrically conductingplate.

In the aforesaid LED structure, the first substrate is a transparentsubstrate and the adhering layer is a transparent adhering layer, and amirror layer is formed on the second surface.

In the aforesaid LED structure, the adhering layer is a transparentadhering layer, and a mirror layer is formed between the first substrateand the adhering layer.

In the aforesaid LED structure, a submount has a third surface whereonat least two third electrically conducting plates and at least twofourth electrically conducting plates are formed, wherein the submountis formed with a plurality of traces for electrically connecting thethird electrically conducting plates and the fourth electricallyconducting plates, each of the third electrically conducting plates andthe fourth electrically conducting plates being electrically connectedto the corresponding fifth electrically conducting plate and/or thesixth electrically conducting plate via one or more solder joints, andthe first substrate being a transparent substrate while the adheringlayer being a transparent adhering layer.

In the aforesaid LED structure, a mirror layer is formed on the submountwhile not covering the third and fourth electrically conducting plates.

In the aforesaid LED structure, a mirror layer is formed on the secondisolation layer.

In the aforesaid LED structure, surfaces of the fifth electricallyconducting plates and the sixth electrically conducting plates have anidentical altitude.

In the aforesaid LED structure, a second conductor layer is formed withat least one conductor and covers the second isolation layer, eachconductor having two opposite ends electrically connected to the fifthelectrically conducting plate and the sixth electrically conductingplate of different units, respectively.

As compared with the conventional devices, the present inventionprovides evident advantages and beneficial effects. Through thepreviously described configurations, the present invention provides atleast the following virtues and functions.

First, the present invention enables convenient interconnection betweenLEDs, and easy manufacture of LED single-structures operable in ahigh-voltage environment, thereby improving utility of the LEDstructure.

Secondly, an LED structure according to the present invention can beproduced through a simple semiconductor process. In such LED structure,since only a submount requires an additional mask and the existingprocess is applicable to the disclosed LED structure, the cost isrelatively low and thus the manufacture is beneficial, thereby ensuringindustrial applicability of the present invention.

In addition, since an interconnection layout between the LED structuresof the present invention is achievable by using submounts, design ofjunction circuits is simplified.

Furthermore, as compared with metal-to-metal adherence that requireshigh heat operation, the adhering layer of the present invention needsonly economical low-temperature operation and provides the advantages oflow costs and high yield.

At last, the present invention facilitates simplifying the junctioncircuit and enables high-voltage LED chips being compact and having highluminance, thereby downsizing and lightening resultant LED lightingdevices.

To sum up, the present invention provides an LED structure, whichcomprises: a first substrate; an adhering layer formed on the firstsubstrate; first ohmic contact layers formed on the adhering layer;epi-layers formed on the first ohmic contact layers; a first isolationlayer covering the first ohmic contact layers and the epi-layers atexposed surfaces thereof; and first electrically conducting plates andsecond electrically conducting plates both formed in the first isolationlayer and electrically connected to the first ohmic contact layers andthe epi-layers, respectively. The first trenches or the second trenchesallow the LED structure to facilitate complex serial/parallel connectionso as to achieve easy and various applications of the LED structure inthe form of single structures under a high-voltage environment. Thepresent invention provides the previously recited advantages andpractical effects while presenting significant structural and functionalimprovements, thus realizing remarkable progress in technology andproducing useful functions. Besides, as compared with the conventionalLED structures, the present invention provides improved and outstandingvirtues, and thus is more practical and industrially applicable.Therefore, the subject matter of the present invention is exactly novel,advanced and functional.

While the above description is merely a summary of the technicalapproach according to the present invention, for further illustratingthe technical means proposed by the present invention allowing peopleskilled in the art to use the present invention, and clarifying theabove and other objectives, features and advantages of the presentinvention, some preferred embodiment will be given below with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic drawing showing a first substrate and apre-processing LED structure to be assembled together.

FIG. 1B is a schematic drawing showing the first substrate and thepre-processing LED structure assembled together.

FIG. 1C is a schematic drawing according to FIG. 1B wherein a temporarysubstrate and an etch-stop layer have been removed therefrom.

FIG. 2 is a sectional view of an LED structure according to oneembodiment of the present invention, showing unit division accomplished.

FIG. 3A is a schematic drawing according to FIG. 2 illustrating a firstetching process.

FIG. 3B is a schematic drawing according to FIG. 3A illustrating asecond etching process successively conducted.

FIG. 4 is a sectional view of the LED structure of FIG. 2 showing afirst isolation layer and electrically conducting plates installed.

FIG. 5A is sectional view of the LED structure assembled to a submountaccording to one embodiment of the present invention.

FIG. 5B is a top view of FIG. 5A.

FIG. 5C is an equivalent circuit diagram according to FIG. 5A.

FIG. 6A is a cross-sectional view of the LED structure having a firstconductor layer according to one embodiment of the present invention.

FIG. 6B is a top view of FIG. 6A.

FIG. 7 is a sectional view of the LED structure according to anotherembodiment of the present invention where unit division, division ofepi-layers, and second trenches have been accomplished.

FIG. 8 is a cross-sectional view showing the LED structure of thepresent invention further assembled with a submount.

FIG. 9 is a cross-sectional view of the LED structure having a secondconductor layer according to the present invention.

FIGS. 10A to 10G provide circuit diagrams of various, exemplificativehigh-voltage LEDs.

 10: pre-processing LED structure  11: temporary substrate  12:etch-stop layer  20: LED structure  21: first substrate 211: firstsurface 212: second surface  22: adhering layer  23: first ohmic contactlayer 231: exposed portion  24: epi-layer 241: lower cladding layer 242:active layer 243: upper cladding layer  25: first isolation layer 251:first opening 252: second opening  26: first electrically conductingplate  27: second electrically conducting plate  28: LED 291: firsttrench 292: second ohmic contact layer 293: first conductor layer  30:LED structure  31: second isolation layer  32: fifth electricallyconducting plate  33: sixth electrically conducting plate 331: extendingportion  34: second trench  35: third opening  36: fourth opening  37:second conductor layer  50: submount  51: third surface  52: thirdelectrically conducting plate  53: fourth electrically conducting plate 60: solder joint A1, A2, A3 . . . : unit B1, B2, B3 . . . : unit

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

To further illustrate the technical means and effects provided by thepresent invention to achieve the intended objective, the specific means,configurations, features and virtues of the LED structure proposed bythe present invention will be explained below through the preferredembodiments with reference to the accompanying drawings.

While the features and the executive details of the present inventionare to be read in conjunction with the accompanying drawings, it is tobe understood that layers contained in the LED structure are madethrough the known semiconductor manufacturing techniques which need noto be described in any length herein. Besides, for eliminatingsuperfluous descriptions, in the following descriptions, the term,“etching process” or “etching method”, is defined as a synonym to acomplete photolithography process. It is also to be noted that thenumber of LEDs used in the present invention is not limited to thoseshown in the following embodiments, but may freely form LED arrays withvarious dimensions.

FIRST PREFERRED EMBODIMENT

Please refer to FIGS. 1A, 1B and 1C for a schematic drawing showing aconventional first substrate 21 and a pre-processing LED structure 10 tobe assembled together, a schematic drawing showing the first substrate21 and the pre-processing LED structure 10 assembled together, and aschematic drawing according to FIG. 1B showing a temporary substrate 11and an etch-stop layer 12 removed therefrom.

Conventionally, the pre-processing LED structure 10 that will laterreceive unit division, isolation layer formation and electricallyconducting plate installation is formed on a wafer through asemiconductor process. However, since being undesirably thick and opaqueand thus unfavorable to practical applications of the LED structure, thewafer has to be removed later. In other words, the wafer is a substratefor temporary use during the process for constructing the LED structure,and thus is herein referred to as the temporary substrate 11.

Among the known methods for removing the temporary substrate 11, etchingwould be the most popular method. For protecting the LED structure frombeing damaged under excessive etching, the etch-stop layer 12 isprovided. The etch-stop layer 12 would be mostly etched during the waferetching process, and thus facilitates protecting the LED structure. Thepre-processing LED structure 10 can be produced through the aboveprocedures.

Please refer to FIGS. 2 to 6C for the LED structure 20 according to oneembodiment of the present invention. The LED structure 20 includes afirst substrate 21, an adhering layer 22, at least two first ohmiccontact layers 23, at least two epi-layers 24, a first isolation layer25, at least two first electrically conducting plates 26, and at leasttwo second electrically conducting plates 27.

The first substrate 21 has a first surface 211 and a second surface 212and primarily serves to support the whole LED structure 20. The firstsubstrate 21 may be a monocrystal substrate, a polycrystal substrate, ora noncrystal substrate, such as a substrate made of glass, sapphire,SiC, GaP, GaAsP, ZnSe, ZnS, AmSSe, etc. Besides, the first substrate 21may be a transparent substrate or an opaque substrate depending on thedesired light-emitting directions or mirror-layer arrangement of the LEDstructure 20. When dual-direction light-emitting allowingupward/downward light-emitting is desired, the first substrate 21 has tobe transparent.

The adhering layer 22 is formed on the first surface 211 for combiningthe first substrate 21 and the first ohmic contact layers 23. Theadhering layer 22 is one selected from B-staged benzocyclobutene (BCB),epoxy, silicone, polymethyl methacry (PMMA), a polymer, spin-on glass(SOG), etc. The adhering layer 22 may be a transparent adhering layer oran opaque adhering layer depending on the light-emitting directions ormirror-layer arrangement of the LED structure 20. When dual-directionlight-emitting allowing upward/downward light-emitting is desired, theadhering layer 22 has to be transparent.

FIG. 2 is a sectional view of the LED structure 20 after unit division.Each of LEDs 28 according to the present invention includes the firstohmic contact layer 23 and the epi-layer 24 settled on the common firstsubstrate 21 and adhering layer 22. Thus, unit division has to beperformed on only the first ohmic contact layers 23 and the epi-layers24 to form units as indicated by A1, A2 and A3 of FIG. 2 or indicated byB1, B2 and B3 of FIG. 6A.

The first ohmic contact layers 23 are formed on the adhering layer 22.Each of the first ohmic contact layers 23 may be a p-type ohmic contactlayer. Besides, the first ohmic contact layers 23 initially formed onthe wafer may be divided into units through the etching method.

Each of the epi-layers 24 is an LED 28 single-structure and may be alsodivided into units through the etching method. A first trench 291 isformed on the epi-layer 24 through an etching process. The first trench291 causes an exposed portion 231 of the first ohmic contact layer 23 soas to facilitate installing the second electrically conducting plate 27.Due to the second electrically conducting plates 27, the LEDs 28 of thedifferent units can be easily connected in serial/parallel, therebyallowing easy fabrication of high-voltage LEDs 28.

Please refer to FIGS. 3A and 3B. FIG. 3A is a schematic drawingaccording to FIG. 2 illustrating a first etching process. FIG. 3B is aschematic drawing according to FIG. 3A illustrating a second etchingprocess successively conducted. The unit division of the first ohmiccontact layers 23 and the formation of the first trenches 291 may beachieved through different etching procedures. Among plural etchingapproaches, one convenient approach is to form two gaps corresponding tointervals between the first ohmic contact layers 23 through a firstetching process and then broaden the gaps to the intended width of thefirst trenches 291 through a second etching process.

Each said epi-layer 24 includes at lease a lower cladding layer 241, anactive layer 242 and an upper cladding layer 243. Each said lowercladding layer 241 is formed on one said first ohmic contact layer 23.The lower cladding layer 241 may be a p-type AlGaInP cladding layer. Theactive layer 242 is formed on the lower cladding layer 241 and may be inthe form of a single hetero-structure (SH), a double hetero-structure(DH) or multiple quantum wells (MQW). The upper cladding layer 243 isformed on the active layer 242 and may be an n-type AlGaInP claddinglayer. A second ohmic contact layer 292 may be formed between the uppercladding layer 243 and the first electrically conducting plate 26.

FIG. 4 is a sectional view of the LED structure of FIG. 2 wherein thefirst isolation layer 25 and electrically conducting plates are formed.The first isolation layer 25 is made of, for example, SiO, and coversexposed surfaces of the first ohmic contact layers 23 and the uppercladding layers 243, while also being formed between each two adjacentsaid first ohmic contact layers 23. The first isolation layer 25 helpsto not only isolate the LEDs 28 of the different units, but also protectthe LEDs 28 from damage caused by external adverse factors, such asmoisture, thereby maximizing the service life of the LEDs 28. On thefirst isolation layer 25, first openings 251 and second openings 252 areformed at the upper cladding layers 243 and the exposed portions 231 ofthe first ohmic contact layers 23, respectively. The first openings 251and second openings 252 are formed by etching the finished firstisolation layer 25.

Each of the first electrically conducting plates 26 is formed in arelative said first opening 251 and electrically connected to thecorresponding upper cladding layer 243.

Each of the second electrically conducting plates 27 is formed in arelative said second opening 252 at each said unit and electricallyconnected to the corresponding first ohmic contact layer 23.

The first electrically conducting plates 26 and second electricallyconducting plates 27 serve to provide power and thus enable theepi-layers 24 to emit light.

When the LED structure 20 is designed as a face-up structure, the firstsubstrate 21 is a transparent substrate and the adhering layer 22 is atransparent adhering layer. Besides, a mirror layer (not shown) isformed on the second surface 212 of the first substrate 21 so as toreflect the light emitted by the epi-layers 24 and thus achieve betterlight extraction efficiency of the LED structure 20. Alternatively, whenthe adhering layer 22 is a transparent adhering layer and a mirror layer(not shown) is formed between the first substrate 21 and the adheringlayer 22, the light emitted by the epi-layers 24 can be also reflectedand thus better light extraction efficiency of the LED structure 20 canbe also achieved.

FIG. 5A is sectional view of the LED structure 20 assembled to asubmount 50 taken along Line A-A of FIG. 5B. FIG. 5B is a top view ofFIG. 5A. FIG. 5C is an equivalent circuit diagram according to FIG. 5A.The LED structure 20 may further include a submount 50 so as to form aflip-chip structure. In the flip-chip structure, the first substrate 21is a transparent substrate and the adhering layer 22 is a transparentadhering layer. The submount 50 has at least a third surface 51. Thethird surface 51 is formed with at least two third electricallyconducting plates 52 and at least two fourth electrically conductingplates 53. Each of the third electrically conducting plates 52 and thefourth electrically conducting plates 53 is electrically connected tothe corresponding first electrically conducting plate 26 and/or thesecond electrically conducting plate 27 via one or more solder joints60. The third electrically conducting plates 52 and the fourthelectrically conducting plates 53 may be expanded to achieve directelectrical connection. Alternatively, plural traces (not shown) may beprovided on the submount 50 for electrically connecting the thirdelectrically conducting plates 52 and the fourth electrically conductingplates 53. Consequently, a complex circuit layout can be formed throughthe aforesaid bonding manner. The submount 50 allows serial/parallelconnection between LEDs 28 to be formed thereon. Since the submount 50is relatively flexible in area and thickness, it caters for even a verycomplicated circuit layout, thereby promising the improved variety ofthe LED structure 20 to meet various applications.

The submount 50 may be a silicon substrate, a printed circuit board(PCB), or a ceramic substrate. For example, the submount 50 may be madeof Al₂O₃, AlN, BeO, low temperature cofired ceramic (LTCC) or hightemperature cofired ceramic (HTCC).

In the flip-chip structure, for obtaining better light extractionefficiency of the LEDs 28, a mirror layer may be further formed on thethird surface 51 of the submount 50 while not covering the thirdelectrically conducting plates 52 and the fourth electrically conductingplates 53. Alternatively, a mirror layer may be formed on the firstisolation layer 25. That is, a mirror layer may be formed on exposedsurfaces of the first isolation layer 25.

The mirror layers may be made of Al, Ag, Au, etc. It is to be noted thatwhen the mirror layer is electrically conductive, it should contactneither the third electrically conducting plates 52 nor the fourthelectrically conducting plates 53 and it should contact neither thefirst electrically conducting plates 26 nor the second electricallyconducting plates 27. More preferably, the mirror layer is separatedfrom each of the electrically conducting plates by a certain distance soas to prevent short circuits between the electrically conducting plates.

Please refer to FIGS. 6A and 6B. FIG. 6A illustrates the LED structure20 with a first conductor layer 293 and is taken along Line B-B of FIG.6B. FIG. 6B is a top view of FIG. 6A. Therein, the LED structure 20further includes the first conductor layer 293. The first conductorlayer 293 is formed with at least one conductor and covers the firstisolation layer 25. Besides, two ends of the conductor are connected tothe second electrically conducting plate 27 and the first electricallyconducting plate 26 of different units, respectively. Thereby, the LEDs28 can be easily connected in serial/parallel. With the support from thefirst isolation layer 25, the first conductor layer 293 can be freelydesigned to cater for a complex circuit layout.

SECOND PREFERRED EMBODIMENT

Please refer to FIGS. 7 to 9 for the LED structure 30 according toanother embodiment of the present invention. The LED structure 30includes a first substrate 21, an adhering layer 22, at least two firstohmic contact layers 23, at least two epi-layers 24, a second isolationlayer 31, at least two fifth electrically conducting plates 32, and atleast two sixth electrically conducting plates 33.

The LED structure 30 of the present embodiment may be also made throughthe process for the first embodiment as shown in FIGS. 1A to 1C.Similarly, the first substrate 21 with the adhering layer 22 attachedthereto is bound with the pre-processing LEDs 28. Then the temporarysubstrate 11 and the etch-stop layer 12 are removed therefrom by etchingso as to obtain the pre-unit-division LED structure 30.

The first substrate 21 has a first surface 211 and a second surface 212and primarily serves to support the whole LED structure 30. The firstsubstrate 21 may be a monocrystal substrate, a polycrystal substrate, ora noncrystal substrate, such as a substrate made of glass, sapphire,SiC, GaP, GaAsP, ZnSe, ZnS, AmSSe, etc. Besides, the first substrate 21may be a transparent substrate or an opaque substrate depending on thedesired light-emitting directions or mirror-layer arrangement of the LEDstructure 30. When dual-direction light-emitting allowingupward/downward light-emitting is desired, the first substrate 21 has tobe transparent.

The adhering layer 22 is formed on the first surface 211 for combiningthe first substrate 21 and the first ohmic contact layers 23. Theadhering layer 22 is one selected from B-staged benzocyclobutene (BCB),epoxy, silicone, polymethyl methacry (PMMA), a polymer, and spin-onglass (SOG). The adhering layer 22 may be a transparent adhering layeror an opaque adhering layer depending on the light-emitting directionsor mirror-layer arrangement of the LED structure 30. When dual-directionlight-emitting allowing upward/downward light-emitting is desired, theadhering layer 22 has to be transparent.

FIG. 7 is a sectional view of the LED structure 30 wherein unitdivision, division of epi-layers 24, and second trenches 34 have beenaccomplished. Since the LED structures 30 according to the presentembodiment also share the common first substrate 21 and adhering layer22, unit division has to be performed on only the first ohmic contactlayers 23 and the epi-layers 24 so as to form units as indicated by A1,A2 and A3.

The first ohmic contact layers 23 are formed on the adhering layer 22.Each of the first ohmic contact layers 23 may be a p-type ohmic contactlayer. Besides, the first ohmic contact layers 23 initially formed onthe wafer may be divided into the units through the etching method.

Each of the epi-layers 24 is an LED 28 single-structure and may be alsodivided into units through the etching method. Each said epi-layer 24includes a lower cladding layer 241, an active layer 242, an uppercladding layer 243 and a second trench 34.

Each said lower cladding layer 241 is formed on one said first ohmiccontact layer 23. The lower cladding layer 241 may be a p-type AlGaInPcladding layer.

The active layer 242 is formed on the lower cladding layer 241 and maybe in the form of a single hetero-structure (SH), a doublehetero-structure (DH) or multiple quantum wells (MQW).

The upper cladding layer 243 is formed on the active layer 242 and maybe an n-type AlGaInP cladding layer.

The second trench 34 is formed through an etching process. The secondtrench 34 vertically passes through the upper cladding layer 243 and theactive layer 242, and enters a part of the lower cladding layer 241. Thesecond trench 34 enables electrical isolation between the active layers242 and the upper cladding layers 243 at its two sides. For the sack ofconvenient production, the second trench 34 may be such formed that thesixth electrically conducting plate 33 is encircled therein so that theactive layers 242 can be effectively isolated while an extending portion331 of the sixth electrically conducting plate 33 successively conductsthe power to the first ohmic contact layers 23. Besides, forfacilitating successive processes, when the second isolation layer 31 isformed, the second trenches 34 can be filled with the second isolationlayer 31.

The second isolation layer 31 is made of, for example, SiO. The secondisolation layer 31 covers exposed surfaces of the upper cladding layers243, while also being formed between each two adjacent said epi-layers24 and any two adjacent said first ohmic contact layers 23. The secondisolation layer 31 helps to not only isolate the LEDs 28 of thedifferent units, but also protect the LEDs 28 from damage caused byexternal adverse factors, such as moisture, thereby maximizing theservice life of the LEDs 28. On the second isolation layer 31, thirdopenings 35 and fourth openings 36 are formed at the upper claddinglayers 243 and inner sides of the second trenches 34, respectively. Thethird openings 35 and fourth openings 36 are formed by etching thefinished second isolation layer 31.

Each of the fifth electrically conducting plates 32 is formed in arelative said third opening 35 and electrically connected to thecorresponding upper cladding layer 243. In addition, a second ohmiccontact layer 292 may be formed between the upper cladding layer 243 andthe fifth electrically conducting plate 32.

Each of the sixth electrically conducting plates 33 is formed in arelative said fourth opening 36 and has an extending portion 331extending downward. The extending portion 331 vertically passes throughthe epi-layer 24 and electrically connected to the corresponding firstohmic contact layer 23. The fifth electrically conducting plates 32 andsixth electrically conducting plates 33 serve to provide power and thusenable the epi-layers 24 to emit light.

When the LED structure 30 is designed as a face-up structure, the firstsubstrate 21 is a transparent substrate and the adhering layer 22 is atransparent adhering layer. Besides, a mirror layer is formed on thesecond surface 212 of the first substrate 21 so as to reflect the lightemitted by the epi-layers 24 and thus achieve better light extractionefficiency of the LED structure 30. Alternatively, when the adheringlayer 22 is a transparent adhering layer and a mirror layer is formedbetween the first substrate 21 and the adhering layer 22, the lightemitted by the epi-layers 24 can be also reflected and thus better lightextraction efficiency of the LED structure 30 can be also achieved.

FIG. 8 is sectional view of the LED structure 30 of the presentinvention assembled to a submount. The LED structure 30 further includesthe submount 50 so as to form a flip-chip structure. In the flip-chipstructure, the first substrate 21 is a transparent substrate and theadhering layer 22 is a transparent adhering layer. The submount 50 hasat least a third surface 51. The third surface 51 is formed with atleast two third electrically conducting plates 52 and at least twofourth electrically conducting plates 53. Each of the third electricallyconducting plates 52 and the fourth electrically conducting plates 53 iselectrically connected to the corresponding fifth electricallyconducting plate 32 and/or the sixth electrically conducting plate 33via one or more solder joints 60. The third electrically conductingplates 52 and the fourth electrically conducting plates 53 may beexpanded to achieve direct electrical connection. Alternatively, pluraltraces (not shown) may be provided on the submount 50 for electricallyconnecting the third electrically conducting plates 52 and the fourthelectrically conducting plates 53. Consequently, a complex circuitlayout can be formed through the aforesaid bonding manner. The submount50 allows serial/parallel connection between LEDs 28 to be formedthereon. Since the submount 50 is relatively flexible in area andthickness, it caters for even a very complicated circuit layout, therebypromising the improved variety of the LED structure 30 to meet variousapplications.

The submount 50 may be a silicon substrate, a printed circuit board(PCB), or a ceramic substrate. For example, the submount 50 may be madeof Al₂O₃, AlN, BeO, low temperature cofired ceramic (LTCC) or hightemperature cofired ceramic (HTCC).

In the flip-chip structure, for obtaining better light extractionefficiency of the LEDs 28, a mirror layer may be further formed on thethird surface 51 of the submount 50 while not covering the thirdelectrically conducting plates 52 and the fourth electrically conductingplates 53. Alternatively, a mirror layer may be formed on the secondisolation layer 31. That is, a mirror layer may be formed on exposedsurfaces of the second isolation layer 31.

The mirror layers may be made of Al, Ag, Au, etc. It is to be noted thatwhen the mirror layer is electrically conductive, it should contactneither the third electrically conducting plates 52 nor the fourthelectrically conducting plates 53 and it should contact neither thefifth electrically conducting plates 32 nor the sixth electricallyconducting plates 33. More preferably, the mirror layer is separatedfrom each of the electrically conducting plates by a certain distance soas to prevent short circuits between the electrically conducting plates.

For easy interconnection between the LEDs 28 of the LED structure 30,and for neat and integral combination between the LED structure 30 andthe submount 50, all surfaces of the fifth electrically conductingplates 32 and the sixth electrically conducting plates 33 have the samealtitude, thereby facilitating operation of the process.

FIG. 9 illustrates the LED structure 30 with a second conductor layer37. Therein, the LED structure 30 further includes the second conductorlayer 37. The second conductor layer 37 is formed with at least oneconductor and covers the second isolation layer 31. Besides, two ends ofthe conductor are connected to the fifth electrically conducting plate32 and the sixth electrically conducting plate 33 of different units,respectively. Thereby, the LEDs 28 can be easily connected inserial/parallel. With the support from the second isolation layer 31,the second conductor layer 37 can be freely designed to cater for acomplex circuit layout.

FIGS. 10A to 10G provide circuit diagrams of various, exemplificativehigh-voltage LEDs 28 according to the present invention. Since the LEDstructure of the present invention has the integral first or secondisolation layer 25 or 31, the complicated circuit layouts as shown inFIG. 10A to 10G can be easily made on the first or second isolationlayer 25 or 31. Particularly, when the submount 50 is implemented toform the flip-chip structure, achievement of these circuit layouts canbe even more available.

The present invention has been described with reference to the preferredembodiment and it is understood that the embodiments are not intended tolimit the scope of the present invention. Moreover, as the contentsdisclosed herein should be readily understood and can be implemented bya person skilled in the art, all equivalent changes or modificationswhich do not depart from the concept of the present invention should beencompassed by the appended claims.

INDUSTRIAL APPLICABILITY

The present invention is related to an LED structure. The LED structureof the present invention comprises: a first substrate; an adhering layerformed on the first surface; first ohmic contact layers formed on theadhering layer; epi-layers formed on the first ohmic contact layers; afirst isolation layer covering exposed surfaces of the first ohmiccontact layers and the epi-layers; and first electrically conductingplates and second electrically conducting plates formed in the firstisolation layer and electrically connected to ends of the first ohmiccontact layer and the epi-layer. By implementing the above technicalmeans, the present invention features for at least the followingadvantages and benefits related to industrial applications:

1. The first trench and the second trench allow the LED structure tofacilitate complex serial/parallel connection so as to achieve easy andvarious applications of the LED structure in the form of singlestructures under a high-voltage environment.

2. The present invention enables convenient interconnection betweenLEDs, and easy manufacture of LED single-structures operable in ahigh-voltage environment, thereby improving utility of the LEDstructure.

3. An LED structure according to the present invention can be producedthrough a simple semiconductor process. In such LED structure, sinceonly a submount requires an additional mask and the existing process isapplicable to the disclosed LED structure, the cost is relatively lowand thus the manufacture is beneficial, thereby ensuring industrialapplicability of the present invention.

4. Since an interconnection layout between the LED structures of thepresent invention is achievable by using submounts, design of junctioncircuits is simplified.

5. As compared with metal-to-metal adherence that requires high heatoperation, the adhering layer of the present invention needs onlyeconomical low-temperature operation and provides the advantages of lowcosts and high yield.

6. The present invention facilitates simplifying the junction circuitand enables high-voltage LED chips being compact and having highluminance, thereby downsizing and lightening resultant LED lightingdevices.

1. An LED structure, comprising: a first substrate having a firstsurface and a second surface; an adhering layer formed on the firstsurface; at least two first ohmic contact layers formed on the adheringlayer; at least two epi-layers wherein a first trench is formed betweeneach two adjacent said epi-layers, and each said epi-layer includes: alower cladding layer formed on one said first ohmic contact layer; anactive layer formed on the lower cladding layer; and an upper claddinglayer formed on the active layer; a first isolation layer coveringexposed surfaces of the first ohmic contact layers and the uppercladding layers, and formed between each two adjacent said first ohmiccontact layers, wherein the first isolation layer has first openings andsecond openings formed at the exposed surfaces of the upper claddinglayers and the first ohmic contact layers, respectively; at least twofirst electrically conducting plates, each formed in one said firstopening and electrically connected to one said upper cladding layer; andat least two second electrically conducting plates, each formed in onesaid second opening and electrically connected to one said first ohmiccontact layer.
 2. The LED structure of claim 1, wherein each of thefirst ohmic contact layers is a p-type ohmic contact layer.
 3. The LEDstructure of claim 1, wherein the lower cladding layer is a p-typeAlGaInP cladding layer and the upper cladding layer is an n-type AlGaInPcladding layer.
 4. The LED structure of claim 1, wherein the activelayer is in a form of a single hetero-structure (SH), a doublehetero-structure (DH) or multiple quantum wells (MQW).
 5. The LEDstructure of claim 1, wherein a second ohmic contact layer is formedbetween the upper cladding layer and the first electrically conductingplates.
 6. The LED structure of claim 1, wherein the first substrate isa transparent substrate and the adhering layer is a transparent adheringlayer, and a mirror layer is formed on the second surface.
 7. The LEDstructure of claim 1, wherein the adhering layer is a transparentadhering layer, and a mirror layer is formed between the first substrateand the adhering layer.
 8. The LED structure of claim 1, furthercomprising a submount that has a third surface whereon at least twothird electrically conducting plates and at least two fourthelectrically conducting plates are formed, wherein the submount isformed with a plurality of traces for electrically connecting the thirdelectrically conducting plates and the fourth electrically conductingplates, each of the third electrically conducting plates and the fourthelectrically conducting plates being electrically connected to thecorresponding first electrically conducting plate and/or the secondelectrically conducting plate via one or more solder joints, and thefirst substrate being a transparent substrate while the adhering layerbeing a transparent adhering layer.
 9. The LED structure of claim 8,wherein a mirror layer is formed on the third surface while not coveringthe third and fourth electrically conducting plates.
 10. The LEDstructure of claim 8, wherein a mirror layer is formed on the firstisolation layer.
 11. The LED structure of claim 1, further comprising afirst conductor layer that is formed with at least one conductor andcovers the first isolation layer, each conductor having two oppositeends electrically connected to the second electrically conducting plateand the first electrically conducting plate of different units,respectively.
 12. An LED structure, comprising: a first substrate havinga first surface and a second surface; an adhering layer formed on thefirst surface; at least two first ohmic contact layers formed on theadhering layer; at least two epi-layers, wherein each said epi-layerincludes: a lower cladding layer formed on one said first ohmic contactlayer; an active layer formed on the lower cladding layer; an uppercladding layer formed on the active layer; and a second trenchvertically passing through the upper cladding layer and the active layerand entering a part of the lower cladding layer; a second isolationlayer covering the upper cladding layers and formed between each twoadjacent said epi-layers and between each two adjacent said first ohmiccontact layers, wherein the second isolation layer has a third openingformed on each said upper cladding layer and a fourth opening formed atan inner side of each said second trench; at least two fifthelectrically conducting plates, each formed in one said third openingand electrically connected to one said upper cladding layer; and atleast two sixth electrically conducting plates, each formed in one saidfourth opening, having an extending portion extending downward tovertically pass through the epi-layer and electrically connect with thefirst ohmic contact layer.
 13. The LED structure of claim 12, whereineach of the first ohmic contact layers is a p-type ohmic contact layer.14. The LED structure of claim 12, wherein the lower cladding layer is ap-type AlGaInP cladding layer and the upper cladding layer is an n-typeAlGaInP cladding layer.
 15. The LED structure of claim 12, wherein theactive layer is in a form of a single hetero-structure (SH), a doublehetero-structure (DH) or multiple quantum wells (MQW).
 16. The LEDstructure of claim 12, wherein the second trench has the secondisolation layer formed therein.
 17. The LED structure of claim 12,wherein a second ohmic contact layer is formed between the uppercladding layer and the fifth electrically conducting plate.
 18. The LEDstructure of claim 12, wherein the first substrate is a transparentsubstrate and the adhering layer is a transparent adhering layer, and amirror layer is formed on the second surface.
 19. The LED structure ofclaim 12, wherein the adhering layer is a transparent adhering layer,and a mirror layer is formed between the first substrate and theadhering layer.
 20. The LED structure of claim 12, further comprising asubmount that has a third surface whereon at least two thirdelectrically conducting plates and at least two fourth electricallyconducting plates are formed, wherein the submount is formed with aplurality of traces for electrically connecting the third electricallyconducting plates and the fourth electrically conducting plates, each ofthe third electrically conducting plates and the fourth electricallyconducting plates being electrically connected to the correspondingfifth electrically conducting plate and/or the sixth electricallyconducting plate via one or more solder joints, and the first substratebeing a transparent substrate while the adhering layer being atransparent adhering layer.
 21. The LED structure of claim 20, wherein amirror layer is formed on the submount while not covering the third andfourth electrically conducting plates.
 22. The LED structure of claim20, wherein a mirror layer is formed on the second isolation layer. 23.The LED structure of claim 12, wherein surfaces of the fifthelectrically conducting plates and the sixth electrically conductingplates have an identical altitude.
 24. The LED structure of claim 12,further comprising a second conductor layer that is formed with at leastone conductor and covers the second isolation layer, each conductorhaving two opposite ends electrically connected to the fifthelectrically conducting plate and the sixth electrically conductingplate of different units, respectively.